Apparatus for orienting quartz crystals by x-rays



F. E. HAWORT'H Dec. 28, 1948.

3 Sheets-Sheet 1 Filed July 9, 1945 FIG.

lNVEN 70/? /-T E. HA WORTH INCIDENT X-RAV BEAM 24g J] A fro/aver Dec. 28, 1948. F. E. HAWORTl l APPARATUS FOR- ORIENTING QUARTZ CRYSTALS BY X-RAYS 3 Sheets-Sheet 2 Filed July 9,- 1945 //vvE/v TOR E E HA WORTH ATTORNEY Dec. 28, 1948. F. E. HAWORTH 2,457,555

APPARATUS FOR QRIENTING QUARTZ CRYSTALS BY X-RAYS 5 She'ets-Sheet 5 Filed July 9, 1945 FIG. 8

uvvavrop F.' E. HAWORTH A TTORNEV Patented Dec. 28, 1948 APPAitAT sFoR-oRIE- 'HNG UARTZ I 'GRYSTALS BY x-nAYs Fran is E. .Iiawiir'th, summ t, .s. ,i ,assirfior a Bell Telephone Laboratories};

corpprated, New

Yar N. Y., a; ,corpora-tionof'fiewyork .Ap'pliea'tionJnly 9, 1945, Serial Nasoaess SClaiins. (01.550 53) This invention relates to a method of and apparatus for examining crystals and, more particularly, to amethod-of and apparatusfor examining quartz piezoelectric crystals by X-rays.

An object of the invention is to facilitate the examination and analysis of crystals.

Another object'of the invention is to facilitate' the production of quartz pieioelectric crystal plates and to improve the uality-thereof.

A still furtherobject of the invention is to simplify and facilitate the process of orienting quartz crystals by X-iays;

Quartz elements, commonly in the form' of wafers and generally referred to as crystal plates or crystals, are used in large numbers at present in many important connections. For example, such elements are used inradio transmitters to maintain the output thereof at its exact assigned frequency value, inelectricalwave filters, radio receivers, frequency standards and many other similar applications. These plates are usually cut from the mother crystal, i'. e. the natural quartaat various orientations with respect to oneor more of the three sets of crystallographic axes thereof. nor egam le, one such plate is produced, as described indetailin Patent 2,268,365, issued December 30, 1941 1110 G. W. Willard, by cutting; the plate not; the natural crystal so oriented that the major surfaces of the plate are inclined +38 degrees with respect to the Z, or optic, axis of; the natural'c-rystal and are parallel" to an X, or electric, axis thereof. Other plates may be inclined various amounts in one or the other direction'with respectto other ages of the mother crystal-depending upon theparticular characteristics desired in the finished plate.

It is obvious from theabove that the production of crystal plates involves analysis of the natural crystal in orderto determine various facts relative to the internal structure, particularly the direction of the-crystallographic axes. If the quartz be well faced, i. e.-if the natural faces have been retained, it is a fairly simpleprocedure to locate the several sets of axes. Crystals of; this type are now quite rare however and arrest of the crystals encountered areiof-thej. so -.callecl river quartz variety, i.- e.- crystalsthe natural faces of which have'become invisible due towea-r, handling, etc. 7 locating of the variousaxes'is-asomewhatzl gvolved procedure I and- .ma'y; comprehendy forfeit: ample, first the examination of: the; crystalifian immersion conoscope for-location of thez or ,Qfitic axis and, secondly,- additional examinations by X-rays and by opticahiastmments.1torv nat on In thecaseof suchmaterial'tli I ofth electrical (Xe andihechanical (Y) axes.

While tlr'iese' procedures have been so perfected that highly accurate and otherwise satisfactory results are obtained, they are of course somewhat painstaking and time consuming.

i rapliywiththe attendant development and printmg processes, is generally considered too slow for commercial production.

It has also been known for some time (see for eiiariiple page 642.61 Crystallography ,arldPracti'c'al Crystal Measurement, volume 1, by A. E. H. Tutton) that the,Laue pattern may be detected by. a fluorescent screen and this has suggested a method of oriehtation wherein the crystal is moved ttain wane observing the pattern on. a fluorescenrs'c re'en ew the desired pattern has been obtai; "d. While'fthis method of, instantane'ohsbbservation appears attractive in view of timesavedactual trials haveproven somewhat unsatisfactory as it has been found that only a.

relatively few spots are sufiicie'ntly prominent for observation and analysis even by a trained observer and even when the process is carried out in a darkened room. The. latter fact, i. e. the necessity for operating in a darkened room, is in itself a; serious drawback.

The novel arrangement of the present invention provides theadvaiita'ge's resulting from instantaneous observationas previouslysought after without any of the attendant disadvantages previously prevailing such as inadequate pattern, necessity of, operatingiri a darkened room, etc.

A feature of the present invention'is a multielement pattern receiving device fora-enacted X r'ay bea'ms, each separate element ofthe device being individually responsive to the specific beam of, Xerays reflected thereto entirely independent of X-r'ay beams refiected'to any of the other elements, eventhe immediately adjacent elements. A further feature of the invention is a muitielement indicator screen, each element of the screen being individually responsive to the particular energizing force transmitted thereto entirely independent of the energizing forces transmitted to any of the other elements, even the immediately adjacent elements.

In accordance with a specific embodimentoi the invention an arrangement for orienting a quartz crystal is provided which may comprise a suitable source of X-rays and means for movably supporting the crystal in the path of the X-rays. The diffraction (Laue) pattern of the the crystal is displayedon an indicator screen which is'in the form of a bank (large number,

of order of 4,400) of cold cathode glow tubes which I diffraction of the X-rays from various points in the crystal, by pulses of current from a multi-I are selectively energized, in accordance with the element pattern receiver. The pattern receiving device contains a large number ."(corresponding to the number of glow tubes) of sensitive points, each of which may be thought of as a separate Geiger counter.

natural faces missing and which, we will further assume, is to be analyzed preparatory to cutting defi nitely oriented plates therefrom, is shown i mounted on platform 22 being temporarily attached thereto by a suitable agent 23 which, may be, for examp1e,sealing wax. By virtue of the .ball'and socket type of mounting illustrated, plat "form 22 is rotatable and tiltable in a plurality of As a difiracted X-ray beam? strikes one of the points an impulse is transmitted to the corresponding glow tube in the display bank, which corresponding tube will be il1uminated in substantial accordance with the intensity of the diffracted X-rays; i. e. for very low jdiilractions, the tube will merely flicker while for stronger diffractions the tube will glow more frequently with a miximum possible numberof 60 illuminations a second, this being the frequency of the alternating current power supply utilized.

The crystal may be manipulated, while the, diffraction pattern displayed on thebank of tubes is observed, until the desired pattern for a typical orientation of the crystal is obtained. Use of this novel arrangement results in a pattern sufii-, ciently extended to give a complete picture of the crystal-structure and through use of the particular type of novel indicator screen, the pattern may be easily observed under normal conditions of illumination. 7

The term reflection is quite commonly used in the literature interchangeably with .difiractionT in referring to this general subject-matter since X-ray diffraction is like light reflection in that the entering and leaving beams make'equal angles with the reflecting or diffractingatomic planes; it is contemplated in the present instance that the two terms may be used interchangeably.

A thorough understanding of the arrangement contemplated by the present invention as well as appreciation of the various valuable features thereof may be gained from consideration of the following detailed description together with the annexed drawings in which: I

Fig. 1 is a schematic representation of an arrangement, which embodies features of the present invention, being used in examination of a crystalline specimen;

Fig. 2 is a sectional view of a Geiger-Muller counter of a type known in the art;

Fig. 3 is a plan view of a multi-e'lement pattern receiving device, which embodies features of the present invention, a portion of the face being broken away to show anumber of the individual, sensitive "points of the device;

Fig. 4 is a, sectional view, taken online 4-4 of Fig. 3, showing the internal arrangement of the receiver;

Fig. 5 is a plan View of a multi-element indicator screen, which embodies features of the present invention, a sufiicient number of the indi vidual glow tubes being shown so that the arrangement, of the entire bank of tubes will be readily appreciated; n

Fig. 6 is a sectional view, taken on line 6-6 of Fig. 5, showing the arrangement of the individual glow tubes;

Fig.7 is a schematic representation of a pordirections whereby crystal 2i may be adjusted in various directions during analysis until the desired position is achieved.

A suitable source of =X-rays, such as X-ray tube 24, is providedtogether with the usual mounting and shielding appliancesand power supply which it does not appear necessary to describe, for projecting an X'ray' beam to crystal 2!. Preferably all wavelengths of thefwhite radiation are utilized. A suitable apertured shield 25-is [provided for collimating the incident beam dire'ctedto the crystal and, as the backreflection? method (which will'be describedsubsequently) is utilized, the beam is passed through pattern receiver 26 "on its passage to the crystal, receiverZE being providedwith a centrally located aperture Hi to permit passage of the X-ray. beam.

A plurality of (diffracted, or reflected, X-ray beams resultsfromfthe incident beam, the distribution and relative intensity of these beams being in accordance with the internal structure of crysta thatis these reflected'beams, if projec'ted onto a sensitive film, would indicate the diffraction pattern of the crystalin' accordance with the" Laue method.

As Willbe described in detail subsequently, receiving device 2 6, includes a plurality of distinctive sensitive poirit's; each of which is connected by'a suitable electrical transmission line to a corresponding ,tube; in thebank of glow tubes provided on-indicator'screen 32. Three of these connectingylines 33, M and: 35, are shown in Fig. In" manner "that? will be described in detail subsequently, each sensitive point of receiver deviceifi that is"struckby a diffracted X-ra'y beam causes the transmission of an impulse over its respective line to the corresponding glow tube in screen 32 to cause 'energization of said corresponding glow tubein the manner previously referred to. A'pattern caused by the illumination" of a plurality'oi the-tubes of screen 32 results therefore which isindic'ative of the diffraction pattern of crystal ZLf-The c'rystal'may then be moved about in'various directions on support 22, while the changing pattern on screen 32 is kept under observation, until the-particular pattern is achieved which isindicative of a desired orientation of crystal 2!. l

, Coming now to a more detailed description of certain of the devices contemplated bythe invention, there isshown in FigL'Z, "for purposes of comparison, a Geiger-Muller point counter of a" type previously described in the literature (Zeitung fill Phys. 71-, pages 422-430, 1931, Max Steenbeck; and Journal of thegFranklin Institute, 237, pages 371-384,- 1944; JosephMorgan, for example); *Metalho'using'il l;-is provided with a closure or base 52' ofsuitable insulating material: A suitablelead-in conductor' 5'3; which is terminated by platinum point '54, is led into housing 51 through sleeve '55 which is sealed through base 52. Aperture '56, provided in the upper surface of housing 5| is closed by quartz plate 51, platinum point 54 being positioned opposite plate 51. The housing is filled with a-suita'blegas, use of air at a pressure of 63 millimeters being described in the article referred to above.

The counter may be operated under alternating current or direct current potential, the voltage being such that an extraneous source of ionization is required toinitiate the discharge within the counter. The counter described in the article referred to operated to give a current of 1.6 coulomb per discharge.

The underlying theory of operation of the novel multi-element pick-up device or pattern receiver contemplated by the present invention is generally similar to that or the Geiger point counter of Fig. 2. The contemplated arrange-- ment of the novel receiving device is shown in detail in Figs. 3 and 4. As illustrated, pattern receiver 26 comprises a suitable gas-tight chamber formed by cylindrical shell '6-1 of suitable insulating material, a closure block 62, also of suitable insulating material, and a face plate 63 which, in the present embodiment of the invention, is of beryllium. A plurality of separated Wires which may be steel, platinumor othersuitable material, as wires '64, 6-5 and 66, are sealed through block 6-2 and extend into the chamber to within a shortdistance from the inner surface of plate 63. As pointed out above, a centrally located-aperture 3| extendsthrough thechamber, providing a path therethrough for the incident X-ray beam.

The chamber is filled-with air or'anothersuitable gas at a predetermined suitable pressure. The wires are closely spaced, for example, one wire for'e'ach square millimeter of surface and the number of individual wires may be of the order of 4,400. Each of'the'individual wiresacts as a separate Geiger point, corresponding to platinum point 54 of the device of Fig. 2,'while beryllium' sheet acts as acommon; plate element for all of the points.

Each of the individual wires of'receiver '26 is connected'by a separate conductor to 2. respectively associated glow tube of indicator screen 32. Three ofthese conductors, 33, 34 and are shown in 'Fig. 1; actually, ofcourse, if receiver 26 comprises 4,400 individual wires orpoints, there will likewise be 4,400 individual conductorsconnecting the points to the corresponding tubesof screen 32.

As stated above, the back-reflection method is preferably, although not necessarily, used, i. e. instead of placing thepattern receiver beyond the crystal and receiving the patternafter the.- X-ray beam .passes throughthe crystal, receiving device 26 isplaced on the same side of crystal .2! as the source of X-rays, tube 24,-and the pattern is received as reflected'back from the crystal. Use of the back-reflection methodsubstantially reduces the time necessary for exposure-and eliminates varying results due to varying crystal thicknesses.

Now as the Laue diffraction; pattern of: crystal E l-falls upon plate 63 of receiverlii (Fig.1) ions will be formed at those; positions in the. gas within-the-chamber-which are irradiated by thereflected X-rays of the pattern. The potential across plate-63 and the :points iszsontixed that an instantaneous discharge onrbreakdown will ooour between the plateand each. point: correspond:- ing to the position at which an ion is formed in the gas. A series of impulses are therefore transmitted over the connecting lines to screen 32,, an impulse being transmitted from each. or the individual wires, or points, of device 25 which is ripposite to an ionized position of the device, 1. e., opposite to a point on plate 63 upon which a difiracted X-ray impinges. The series of impulses transmitted to device 32 at any moment therefore, is in accordance with the X-ray pattern reflected by crystal 2| and picked up by device 2-6 at the same moment.

Indicator device, or screen 32,v in one form contemplated by the present invention, is illustrated in detail in Figs. 5 and 6. A plurality of lamps as 8|, 82- and 83, which may be in the form of cold cathode gas-filled tubes of the general type .described in an article, Cold-Cathode Gas-Filled Tubes as Circuit Elements, S. B. Ingram, Electrical Engineering (Transactions), July 1939, vol. 58, page 342, are mounted in a suitable circular block of insulating material. The number and position of the tubes in the bank of screen 32' corresponds to the number and position of the individual wires, or sensitive points, of receiver .26; that is, there is a tube of screen 32 corresponding to, and electrically connected to, each individual wire of receiver 26.

The tubes, as pointed out, above may take the form of cold cathode vacuum tubes of the three element type, i. e., provided with a cathode, a control anode and a main anode. The conduction path between the cathode and the control anode is known as the control gap and the con duction path between the cathodeand the main anode is known as the main gap.

For the present purpose, the tubes are preferably somewhat smaller than the ordinary commercial vacuum tube. The exact size of the tubes is not controlling but it is contemplated, by way'oi example, that tubes-approximately one-half inch. in diameter might be used in which the over-all diameter of the screen, with a total of 4,400 tubes would be of the order of three feet. It is apparent, of course, that the pattern displayed on screen 32, while an exact reproduction of that projected onto receiver 26, will be a considerablyenlarged version thereof. This is a highly desirable feature.

The operation of the glow tubes of indicator screen 32 under control of the pulses set up in pattern receiving device 26 may best be understood by reference tothe'schematic'circuit of Fig. '7. (For purposes of simplicity of disclosure, only two of the glow tubes of indicator screen 32 and two of the sensitive points, or wires, of pattern receiver 26 have been illustrated.) The control anode of each tube is connected over the individual line provided to the respectively associated sensitive point of receiver 26, i. e., as illustrated, control anode 34 of tube 83 is connected by line 33 to its associatedpoint in receiver 26 (for example, this may-be point 64 [Fig 4]) and controlanode 85 oftube'88 is connected over line-35 to its'associated point of the pattern receiver.

A-voltage from alternating current source 9i, the frequency of which will be assumed to be so cycles per second, is applied, through-respective resistances-92 and 93, across the main gap of each tube, for example across main anode 94 and cathode 95 of glow tube 85 and acrossm-a in anode Bland cathode 980i glow-'tube83.

A direct current voltage fromibattery 1H: ii is applied across the con-trol gap of each glowtube and the respective gap of receiver 26 in series. For example, the negative terminal of battery i II is connected to respective cathodes 98 and 95 of tubes 83 and 86 while thepositive terminal of the battery is connected to plate 63 of pattern receiver 26; the respective sensitive points of the receiver are connected to control anodes 84 and 35 of tubes 83 and 86 respectively. This voltage is not, in itself, quite sufficient to cause the glow tubes to trip, or break down, but, when augmented by the additional energy transmitted from pattern receiverzfi when a point is ionized, the voltage applied to the control gap of the respective glow tube will then besufiicient to cause ionization and subsequent breakdown of the main gap of the tube which will then light up or glow. Thus, those sensitive points of pattern receiver 26 which are receiving X-rays will trip-01f the corresponding glow tubes of screen 32 and cause a display thereon corresponding to the difiraction pattern of crystal 2! (Fig. 1). The frequency with which a respective tube is tripped-off will depend upon the intensity of the X-ray diffraction from the corresponding portion of the specimen being analyzed; for very weak difiractions a tube may merely flicker while, as the intensity of the difiracted X-rays increases, the frequency of the tube breakdowns will increase with a possible maximum of 60 per second, the frequency of' power supply 9|, for the stronger diflraotions.

There is illustrated in Fig. 8 the pattern displayed on screen 32 for a typical orientation of a crystal. That is the observer starts the test with the knowledge that the particular orientation of the crystal thathe is seeking will result in the symmerical pattern of Fig. 8. He therefore manipulates the crystal on its mounting (Fig. 1) while observing the pattern on screen 32 until the desired pattern of Fig. 8 is attained. From the "pattern of a crystal displayed on screen 32 there may readily be determined various pertinent facts concerning the crystal,,such as the location and senseof the various crystal lographic axes and the handedness of the crystal. This is true, not only in the case of the mother crystal, but in the oasesof finished and partially completed cuts or plates as well. l The novel arrangement contemplated byth present invention, one specific embodiment of which has just been described in detail above, makes possible the accomplishment in the matter of a few seconds of that which by previous methods takes considerably longer. The orientation of a quartz stone can be determined imme diately with respect to all of the natural crystallographic axes without the necessity of making any cuts in the surface or immersion in a liquid. While a specific embodiment of the invention has been selected for illustration and detailed description, the invention is not, of course, limited in its application to such embodiment. For example, the arrangement is applicable to analysis of crystalline materials other than quartz and types of pattern receivers and display screens other than those described may be utilized. While certain advantages appear to reside in use of the backreflection method, this method need not necessarily be used. Alternating current power supplies of frequency other than 60 cycles per second may be utilized with corresponding change in the maximum possible number of times per second that the respective glow tubes may be tripped-off. In short the embodiment described should be taken as illustrative of the invention and not as restrictive thereof. 4

What is claimed 1. In the analyzation of a quartz crystal} appa ratus for displaying the diffraction'pattern ofthe crystal and received by the sensitivereceiver at the same instant. v

2. Apparatus for orienting a specimen of crystalline material which comprises means for pro- J'ecting a beam of X-rays onto said specimen, means for receiving the Laue pattern of X-rays reflected by said specimen on a selective pattern receiver, a group of individual light sources, and means for selectively energizing-the light sources of said group in accordance with the pattern received by said pattern receiver, said receiving means and said energizing means operating substantially simultaneously and in step.

3. Apparatus for analyzing a crystal of the type capable of emitting a plurality of distinct diffracted X-rays from a single incident X-ray beam, comprising means for adjustably supportnumberof thesensitive areas of said patternreceiver, and means for energizing selected ones of said visual indicators in accordance with the difiraction patternof said crystal received by said pattern receiver, said energizing means operating substantially simultaneously with respect to activation of respective areas of said receiver.

4. Apparatus for analyzing a quartz crystal comprising a source of X-rays, means for adjust-' ably supporting a crystal being analyzed, means for projecting an X-ray beam from said source to said crystal, a pattern receiver for receiving the X-rays diffracted by'said crystal, said receiver comprising a number of the order'of 4,400 of individual sensitive areas each of which is capable of being independently activated by contact'of diffracted X-rays whereby said sensitive areas are activated at any one instantin accordance with theLaue pattern of X-rays diiiracted at that same instantby said crystal being analyzed, aviewing screen comprising a plurality of glow tubes, the arrangement ofsaid glow tubes comprisin said screen corresponding with respectto-number and relative positioning to the arrangement of said sensitive areas of said pattern receivenand means for activating said glow tubes under instantaneous control of said pattern receiver whereby the visual pattern resulting at any one instant from activation of glow tubes of said screen corresponds to the pattern of X-rays difiracted at the same instant by said crystal and received by said pattern receiver.

5. Apparatus for analysis of a crystalline'specimen capable of emitting a plurality'of distinct difiracted X-rays from a single incident X-ray beam, comprising means for projecting an X-ray beam, means for adjustably supporting a crystal to be analyzed in the path of the projected beam, a difiraction pattern receiver comprising a plurality of separate Geiger points, means for supporting said pattern receiver in position to receive the X-ray pattern diffracted by said crystal, a screen of cold cathode glow tubes, means for selectively activating said Geiger points in accordance with the difiraction pattern received and means for individually connecting each of said Geiger points to a respective one of said glow tubes whereby to selectively control the activation of said glow tubes in accordance with the activation of said Geiger points.

6. In apparatus for analysis of a crystalline substance capable of emitting a plurality of distinct diffracted X-rays from a single incident X-ray beam, a Laue pattern receiver for receiving the diffracted X-rays and for translating them into a series of corresponding electrical pulses, said pattern receiver comprising a hermetically sealed chamber, a conductive sheet forming one closure member for said chamber, a plurality of distinct conductive wire-like members within said chamber, all of said wire-like members being spaced a like distance from said conductive sheet and also being spaced a like distance from each other, a gas within said chamber filling the space between said wire-like members and said conductive sheet, and means for applying a potential across said conductive sheet and the individual wire-like members, the magnitude of said applied potential being insufficient in itself to cause a discharge between respective ones of said members and said sheet but being sufiicient to cause such a discharge in response to movement of an ionizing particle between said sheet and a respective one of said members.

7. In apparatus for analysis of a crystalline specimen capable of emitting a plurality of distinct diffracted X-rays from a single incident X-ray beam, a receiver for reception of the reflected X-rays and for translation thereof into a corresponding series of electrical pulses, said receiver comprising a gas-tight chamber, a plurality of equally spaced wires within said chamber, a beryllium plate forming one closure member of said chamber and exposed on one surface to reflected X-rays, the projecting ends of each of said wires being spaced an equal distance from said beryllium plate, a gas within said chamber filling the space between said beryllium plate and the projecting ends of said Wires, and means for applying a potential across said beryllium plate and said wires, the magnitude of said applied voltage being insufficient in itself to cause breakdown between said plate and respective ones of said wires but being sufiicient to cause such breakdown in response to movement of an ionizing particle between said plate and a respective one of said wires.

8. Apparatus for orienting a quartz crystal comprising means for projecting an X-ray beam to said crystal, means for intercepting the Laue pattern of X-rays reflected by said crystal, a bank of glow tubes, means controlled by said intercepting means for activating selected ones of the glow tubes to reproduce an enlarged version of the Laue pattern intercepted by said intercepting means, and means for adjusting said crystal in the path of the projected X-ray beam in order to bring the Laue pattern reproduced on said bank of glow tubes into substantial accord with a predetermined pattern.

FRANCIS E. HAWORTH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,707,486 Kishpaugh Apr. 2, 1929 2,380,235 I-Iarker July 10, 1945 OTHER REFERENCES Cold- Cathode Gas-Filled Tubes as Circuit Elements, S. B. Ingram, E. E. (transactions) July 1939, vol. 58, page 342. 

